FR3019539A1 - MIXED OXIDES AND SULFIDES OF BISMUTH AND COPPER FOR PHOTOVOLTAIC APPLICATION - Google Patents

Abstract

The present invention relates to a material comprising at least one compound of formula Bi1-xMxCu1-y-εM'yOS1-zM "z, processes for the preparation of this material and their use as semiconductors, in particular for photoelectrochemical or photochemical application. The invention also relates to photovoltaic devices using these compounds.

Description

The present invention relates to the field of semiconducting inorganic compounds, in particular intended to provide a photocurrent, in particular by photovoltaic effect. Nowadays, photovoltaic technologies using inorganic compounds are mainly based on silicon technologies (over 80% of the market) and on thin film technologies (mainly CdTe and CIGS (Copper Indium Gallium Selenium), representing 20% of the market). The growth of the photovoltaic market seems exponential (40 GW cumulated in 2010, 67 GW cumulated in 2011).

Unfortunately, these technologies suffer from disadvantages limiting their ability to satisfy this growing market. These disadvantages include poor flexibility in silicon from a mechanical and installation point of view, and toxicity and scarcity of elements for thin-film technologies. In particular, cadmium, tellurium and selenium are toxic. In addition, indium and tellurium are rare, which has a particular impact on their cost. For these reasons, it seeks to overcome the implementation of indium, cadmium, tellurium and selenium or to reduce their proportion.

One way that has been recommended to replace indium in the CIGS is to replace it with the couple (Zn2 +, Sn4 +). In this context, it has been proposed in particular the compound Cu2ZnSnSe4 (called CZTS). This material is today considered the most serious successor of CIGS in terms of efficiency, but which has the disadvantage of toxicity of selenium. With regard to selenium and tellurium, few alternatives have been proposed and they are generally not very interesting. Compounds such as SnS, FeS2 and Cu2S have been well tested but, although they have interesting intrinsic properties (gap, conductivity ...), they do not prove to be sufficiently stable chemically ( eg Cu2S is very easily converted to Cu2O in contact with air and moisture). To date, to the knowledge of the inventors, it has not been published satisfactory solution for obtaining good photovoltaic efficiency without problems related to the toxicity and / or scarcity of the elements used in a photovoltaic system. An object of the present invention is precisely to provide inorganic compounds alternative to those used in current photovoltaic technologies, which make it possible to avoid the aforementioned problems. For this purpose, the present invention proposes to use a new family of inorganic materials, whose inventors have now shown that, unexpectedly, they prove to have good efficiency, and that they have the advantage of not having to use, or at a very low level, rare or toxic metals of the type In, Te, Cd mentioned above, and furthermore offer the possibility of using anions, such as Se or Te, in a reduced content, even not to use this type of anions. One of the objects of the present invention is a novel material comprising at least one compound of formula (I): wherein M is an element or a mixture of elements selected from group (A). ) consisting of Pb, Sn, Hg, Ca, Sr, Ba, Sb, In, Ti, Mg, rare earths, M 'is a member or a mixture of elements selected from the group (B) consisting of Ag, Ti , V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Mg, Al, Cd, M "is a halogen, x, y and z are numbers less than 1, in particular less than 0.6, especially less than 0.5, for example less than 0.2, with at least one of the numbers x, y or z not zero, and 0 E <0.2, where present, the elements M, M 'and M "are generally substitution elements respectively occupying the place of the element Bi, the element Cu and the element S." Material comprising at least one compound of formula (I) ", we mean a solid, usually in form divided (powder, dispersion) or in the form of a coating or a continuous or discontinuous layer on a support, and which comprises, or even consists of, a compound of formula (I). "Rare earth" means the elements of the group constituted by yttrium and scandium and the elements of the Periodic Table with an atomic number inclusive of between 57 and 71. According to the invention, the element M may preferably be selected from the elements Sb, Pb, Ba and rare earths. The element M may for example be lutetium. According to the invention, the element M 'may preferably be chosen from the elements Ag, Zn, Mn. The element M 'may for example be the element Ag. According to the invention, the element M "may in particular be the element I. In a first variant of the invention, the compound of formula (I) according to the The invention has the following formula: Bi M 'OS (la), where x # 0, c is a zero or non-zero number and M is an element or a mixture of elements selected from group (A) consisting of Pb, Sn, Hg, Ca, Sr, Ba, Sb, In, T1, Mg, rare earths According to one embodiment of this variant of the invention, M is an element or a mixture of elements chosen from The compound may then, for example, correspond to the formula Bii, LuxCuOS where x # 0 and E = O. In a second variant of the invention, the compound of formula (I) according to the invention corresponds to the formula following: BiCui_y_EM'yOS (lb), where y # 0, E is a zero or non-zero number and M 'is an element or a mixture of elements selected from the group (B) consisting of Ag, Ti, V, Cr , Mn, Fe, Co, Ni , Zn, Ga, Mg, Al, Cd. According to one embodiment of this variant of the invention, M 'is an element or a mixture of elements chosen from the Ag and Zn elements. The compound can then for example respond to the formula BiCui_yAgyOS or to the formula BiCul_yZnyOS where y # 0 and s = 0. In a third variant of the invention, the compound of formula (I) according to R 2014/032 4 the invention corresponds to the following formula: BiCu0SzM 'i_z (Ic), where z # 0, E is a zero or non-zero number and M "is a halogen According to one embodiment of this variant of the invention, M" is I element, and the compound then responds to the formula BiCu0Szli_z where z # 0 and s = O.

The invention also relates to different access routes to the material according to the invention. Thus, in a first variant, the subject of the invention is a first method for preparing the material according to the invention comprising a step of solid grinding of a mixture comprising at least inorganic compounds of bismuth and copper, and possibly at least an oxide, sulfide, oxysulfide, halide or oxyhalide of at least one element selected from Bi and the elements of group (A) consisting of Pb, Sn, Hg, Ca, Sr, Ba, Sb, In, Tl, Mg, the rare earths, and optionally at least one oxide, sulphide, oxysulphide, halide or oxyhalide of at least one element selected from Cu and elements of the group (B) consisting of Ag, Ti, V, Cr, Mn, Fe, Co , Ni, Zn, Ga, Mg, Al, Cd. According to this variant, a solid form mixture comprising at least inorganic compounds of bismuth and copper is ground. Preferably, the inorganic bismuth and copper compounds present in the mixture are at least Bi203, Bi2S3 and Cu2S. This grinding can be done according to any known means. This mixture can in particular be placed in an agate mortar. The grinding may for example be carried out with a planetary mill. To facilitate grinding, it is possible to add to the mixture in solid form grinding balls which consist, for example, of stainless steel balls, balls of special chromium steel, agate balls, carbide balls, tungsten, balls made of zirconium oxide. The grinding time can be adjusted according to the desired product. It may especially be between 20 minutes and 96 hours, in particular between 1 hour and 30 hours. The inorganic compounds of bismuth and copper in the mixture may be in the form of particles having a particle size less than 50 μm, in particular less than 10 μm, for example less than 1 μm. The particle sizes referred to herein can typically be measured by scanning electron microscopy (SEM). In a second variant, the subject of the invention is a second process for preparing the material according to the invention by carrying out a precipitation reaction comprising the following steps: (a) preparation of at least one solution comprising metal precursors in the form of at least one salt of the inorganic bismuth compounds, and optionally at least one oxide, sulphide, oxysulfide, halide or oxyhalide of at least one element selected from Bi and the elements of the group (A) consisting of Pb, Sn , Hg, Ca, Sr, Ba, Sb, In, Ti, Mg, rare earths, and (b) preparing at least one solution comprising metal precursors in the form of at least one salt of the inorganic copper compounds, and optionally at least one oxide, sulfide, oxysulfide, halide or oxyhalide of at least one element selected from Cu and the elements of group (B) consisting of Ag, Ti, V, Cr, Mn, Fe, Co, Ni , Zn, Ga, Mg, Al, Cd, and, (c) optionally separation of at least one solution comprising a source of sulfur, (d) mixing precipitation of the solutions obtained at the end of steps (a), (b) and optionally (c), (e) filtration, and washing if necessary of the compound of formula (I) obtained at the end of step (d). This method consists in carrying out a precipitation reaction by using soluble metal precursors in order to obtain a homogeneous mixture of the substitution elements in the material comprising the compound of formula (I). The different precursor solutions are prepared separately and then mixed together, whereby a homogeneous mixture and submicron particle sizes are obtained. In certain cases, the precipitation can be carried out by raising the temperature in particular to obtain a better crystallization. As an illustration, such a precipitation can be carried out as follows: (a) - (b) providing a solution of the soluble metal precursors. For example, it is possible to prepare a basic pH solution in which: the elements Bi and of the group (A) are stabilized by complexing with a strongly complexing polycarboxylate anion such as a citrate, lactate or tartrate; copper is stabilized in the form of copper (I) by addition of an excess of reducing agent (such as, for example, sodium thiosulphate, hydrazine, etc.), copper and the elements of group (B) can be kept soluble in basic medium either by the action of basic pH (AI, Zn) or stabilized in basic medium by addition of ligands complexing the ion such as amino ligands (ammonia, ethylene diamine, organic amine ...) . (c) providing a solution comprising a source of sulfur, for example sulphide ions (d) mixing the solutions obtained at the end of steps (a) and (b) with the solution obtained at the end of the step (c). The mixing speed and the temperature of the mixture can be adjusted to control the morphology or size of the solid particles obtained. (e) heating and stirring for a time sufficient to obtain crystallization of the desired compound. The compound is then filtered and washed to remove non-retained ions in the solid composition and is then oven-dried. In a third variant, the subject of the invention is a third method for preparing the material according to the invention comprising the following steps: (a ') providing a mixture comprising at least, in the dispersed state, inorganic compounds of bismuth and copper and optionally at least one oxide, sulfide, oxysulfide, halide or oxyhalide of at least one element selected from Bi and the elements of group (A) consisting of Pb, Sn, Hg, Ca, Sr, Ba, Sb, In, Tl, Mg, the rare earths, and optionally at least one oxide, sulphide, oxysulfide, halide or oxyhalide of at least one element selected from Cu and the elements of the group (B) consisting of Ag, Ti, V , Cr, Mn, Fe, Co, Ni, Zn, Ga, Mg, Al, Cd, and optionally a source of sulfur, (b ') dissolving the mixture in water or an aqueous medium under hydrothermal conditions and preferably with stirring, and (c ') cooling of the resulting solution, whereby one obtains icules of the compound of formula (I) wherein: x, y, z, E are as defined above.

The aqueous medium used in step (b ') can in particular be a solvent, for example a mixture of ethylene glycol or a refluxing ionic liquid. At the end of step (c '), a deagglomeration step can be carried out, for example, by means of an ultrasound probe.

Preferably, the inorganic bismuth and copper compounds provided in the mixture of step (a ') are at least Bi 2 O 3 and Cu 2 O. In another possible embodiment, soluble salts of bismuth and copper may be employed. In particular, in the absence of oxide of the inorganic compounds in step (a '), step (b') is advantageously carried out in the presence of a source of oxygen, such as water, nitrates or even carbonates. The source of sulfur employed in step (a ') may be chosen from sulfur, hydrogen sulphide H2S and its salts, an organic sulfur compound (thiol, thioether, thioamide, etc.), preferably a sulphide of anhydrous or hydrated sodium.

Preferably, irrespective of their exact nature, the oxides in the dispersed state are employed in step (a ') in the form of particles, typically in the form of powders, having a particle size of less than 10 μm, in particular lower than at 5 μm, preferably less than 1 μm. This particle size can for example be obtained by prior grinding of the oxides (separately, or more advantageously in the case of oxide mixtures, this grinding can be carried out on the oxide mixture), for example, using a Micronizer type device or wet ball mill. In step (b '), the dissolution is carried out in "hydrothermal conditions". By hydrothermal conditions in the sense of the present description is meant that the step is conducted at a temperature above 180 ° C under the saturated vapor pressure of water. When grinding is carried out, the temperature of step (b ') may be less than 240 ° C, or even less than 210 ° C, for example between 180 ° C and 200 ° C.

Alternatively, step (b ') can be carried out without preliminary grinding, in which case it is however preferable to carry out the step at a temperature greater than 240 ° C., preferably greater than 250 ° C. Preferably, in step (b '), the mixture is placed in water at a temperature below the hydrothermal conditions (typically at an ambient temperature and under atmospheric pressure), then the temperature is slowly raised. advantageously at a rate of less than 10 ° C./min, for example between 0.5 and 5 ° C./min, typically 2.5 ° C./min, typically operating in a closed medium (using a bomb-type device) hydrothermal, including Parr bomb) until reaching the operating temperature. In step (b '), the dissolution is specifically carried out with stirring. This agitation can be carried out in particular by magnetic stirring, for example by placing the hydrothermal bomb, on a magnetic stirrer, the assembly being placed in a heating chamber (such as an oven).

Step (b ') is conducted for a time sufficient to obtain dissolution. Typically, the temperature is maintained at at least 190 ° C for at least 12 hours, for example for 48 hours, or even 7 days. At the end of the dissolution carried out in step (b '), the solution obtained is, in step (c), typically reduced to an ambient temperature or more generally to a temperature of between 10 and 30 ° C. cooling, for example by decreasing the temperature by at least 1 ° C / min, preferably by a faster cooling, with a reduction typically of at least 3 ° C / min, for example from 3 to 5 ° C / min. This type of cooling typically leads to particles having a length of between 50 nm and 5 μm, typically between 100 nm and 1 μm, and a thickness of 50 nm. Moreover, without wishing to be bound to a particular theory, the above-mentioned high cooling rates generally lead to very low levels of impurities (Cu2S, Bi203 and Cu2BiS3 in particular).

Advantageously, the material according to the invention is obtained by the first solid grinding process described above. The subject of the present invention is furthermore the use of a material comprising at least one compound of formula (I): ## STR1 ## in which M is an element or a mixture of elements chosen from group (A) consisting of Pb, Sn, Hg, Ca, Sr, Ba, Sb, In, Ti, Mg, rare earths, M 'is a member or a mixture of elements selected from the group (B) consisting of R 2014/032 by Ag, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Mg, Al, Cd, M "is a halogen, x, y and z are numbers less than 1, in particular less than 0.6, especially less than 0.5, for example less than 0.2, with at least one of the numbers x, y and z not zero, and 0 <0.2 as a semiconductor, in particular for photoelectrochemical or photochemical application, in particular for providing a photocurrent.

What is indicated in the above description, especially with regard to the elements M, M 'and M ", applies to the present use according to the invention The compound which is present in the semiconductor material is a material substituted inorganic, in particular of the p type.

Chemical substitutions of bismuth, copper and / or sulfur may have several roles. In the case of isoelectronic substitutions such as the substitution of the element Bi by rare earths or by the element Sb or alternatively the substitution of the element Cu by the element Ag, these substitutions can, in particular by modifying the parameters and / or by changing the extension of the orbitals and their energy position, thus causing changes in the gap (valence band - conduction band). The aliovalent substitutions modify the degree of oxidation of the element Cu.

The introduction of substituents in the structure of the semiconductor may, as the case may be, cause a reduction or an increase in the number of charge carriers. The substituted materials may in particular have a higher conductivity, which induces an improved conduction capacity, compared to its unsubstituted form, or conversely a lower conductivity. In the context of the present invention, the inventors have now demonstrated that the materials corresponding to the above formula (I), in particular, when they are p-type, are capable of providing a photocurrent when they are irradiated under a wavelength greater than their gap (ie the generation of an electron-hole pair within the material under the effect of an incident photon of sufficient energy, the charged species formed (1). electron and the "hole", ie the electron gap) being free to move to generate a current).

In particular, the inventors have now demonstrated that the materials of the invention prove to be suitable for ensuring a photovoltaic effect. In general, a photovoltaic effect is obtained by joint implementation of two different type of semiconductor compounds, namely: a first compound having a p-type semiconductor character; and a second compound having an n-type semiconductor character. These compounds are placed close to each other in a manner known per se (ie in direct contact or at least at a sufficiently small distance to ensure the photovoltaic effect) to form a p-n type junction. The electron-hole pairs created by light absorption are dissociated at the pn junction and the excited electrons can be conveyed by the n-type semiconductor towards the anode, the holes being led towards the cathode via the p-type semiconductor. In the context of the invention, the photovoltaic effect is typically obtained by placing a material based on a semiconductor of formula (I) above, which is also specifically of the p type, in contact with a semiconductor n-type between two electrodes, in direct contact or optionally connected to at least one of the electrodes via an additional coating, for example a charge collection coating; and irradiating the photovoltaic device thus produced with adequate electromagnetic radiation, typically by the light of the solar spectrum. To do this, it is preferable that one of the electrodes passes the electromagnetic radiation used. According to another particular aspect, the present invention relates to photovoltaic devices comprising, between a hole-conducting material and an electron-conducting material, a layer based on a compound of formula (I) of type p and a layer based on an n-type semiconductor, wherein: the layer based on the compound of formula (I) is in contact with the layer based on the n-type semiconductor; R 2014/032 11 the layer based on the compound of formula (I) is close to the hole-conducting material; and the n-type semiconductor layer is in proximity to the electron-conducting material.

For the purposes of the present description, the term "hole-conducting material" means a material which is capable of ensuring a flow of current between the p-type semiconductor and the electrical circuit.

The n-type semiconductor employed in the photovoltaic devices according to the invention may be chosen from any semiconductor which exhibits an electron acceptor character which is more marked than the compound of formula (I) or a compound promoting the evacuation of electrons. Preferably, the n-type semiconductor may be an oxide, for example ZnO, or TiO 2, or a sulphide, for example ZnS.

The hole-conducting material used in the photovoltaic devices according to the invention may be, for example, a suitable metal, such as gold, tungsten, or molybdenum; or a metal deposited on a support, or in contact with an electrolyte, such as Pt / FTO (platinum deposited on fluorine-doped tin dioxide); or a conductive oxide such as ITO (tin-doped indium oxide), for example, deposited on glass; or a p-type conductive polymer. According to a particular embodiment, the hole-conducting material may comprise a hole-conducting material of the aforementioned type and a redox mediator, for example an electrolyte containing the 12/1 "pair, in which case the hole-conducting material is typically Pt / FTO The electron-conducting material can be, for example FTO, or AZO (aluminum-doped zinc oxide), or an n-type semiconductor In a photovoltaic device according to the invention, the holes generated at the pn junction are extracted via the hole-conducting material and the electrons are extracted via the electron-conducting material of the aforementioned type.In a photovoltaic device according to the invention, it is preferable that the hole-conducting material and / or the conductive material electrons is at least a partially transparent material that allows the electromagnetic radiation to be passed in. In this case, the material at least s partially transparent is advantageously placed between the source of the incident electromagnetic radiation and the p-type semiconductor.

For this purpose, the hole-conducting material may for example be a material chosen from a metal or a conductive glass. Alternatively or jointly, the electron-conducting material may be at least partially transparent, and is then chosen, for example, from FTO (fluorine-doped tin dioxide), or AZO (aluminum-doped zinc oxide), or a semiconductor. n-type conductor. According to another advantageous embodiment, the layer based on an n-type semiconductor which is in contact with the layer based on a compound of formula (I) of type p may also be at least partially transparent.

By "partially transparent material" is meant here a material which passes at least part of the incident electromagnetic radiation, useful for providing the photocurrent, and which may be: a material which does not fully absorb the incident electromagnetic field; and / or a material which is in a perforated form (typically having holes, slots or gaps) capable of allowing part of the electromagnetic radiation to pass without the latter encountering the material. The compound of formula (I) employed according to the present invention is advantageously used in the form of isotropic or anisotropic objects having at least a dimension of less than 50 μm, preferably less than 20 μm, typically less than 10 μm, and preferably less than 20 μm. 5 μm, generally less than 1 μm, more preferably less than 500 nm, for example less than 200 nm, or even 100 nm.

Typically, the dimension less than 50 μm may be: the average diameter in the case of isotropic objects; thickness or transverse diameter in the case of anisotropic objects. According to a first variant, the objects based on a compound of formula (I) are particles, typically having dimensions less than 10 .mu.m. These particles are preferably obtained according to one of the preparation methods of the invention.

By "particles" is meant here isotropic or anisotropic objects, which may be individual particles, or aggregates. The particle sizes referred to herein can typically be measured by scanning electron microscopy (SEM).

Advantageously, the compound of formula (I) is in the form of platelet-type anisotropic particles, or agglomerates of a few tens to a few hundreds of particles of this type, these platelet-type particles typically having dimensions remaining less than 5 μm. , (preferably less than 1 μm, more preferably less than 500 nm), with a thickness which typically remains less than 500 nm, for example less than 100 nm. Particles of the type described according to the first variant can typically be employed in the state deposited on an n-type conductive or semiconductor support. A plate of ITO or metal covered with particles of formula (I) p type according to the invention can thus, for example play the role of a photoactive electrode for a photoelectrochemical device that can be used in particular as a photodetector. Typically, a photoelectrochemical type device employing a photoactive electrode of the aforementioned type comprises an electrolyte which is generally a salt solution, for example a KCl solution, typically having a concentration of the order of 1 M, in which are dipped: a photoactive electrode of the aforementioned type (ITO plate or metal covered with particles of compound of formula (I) according to the invention); a reference electrode; and a counter electrode; these three electrodes being interconnected, typically by a potentiostat.

According to a possible embodiment, the electrochemical device may comprise: as a photoactive electrode: a support (such as an ITO plate) coated with particles of compound of formula (I); as a reference electrode: for example, an Ag / AgCl electrode; and as a counter-electrode: for example, a platinum wire; these three electrodes being interconnected, typically by a potentiostat. When an electrochemical device of this type is placed under a light source, under the effect of irradiation, electron-hole pairs are formed and are dissociated. When the electrolyte is an aqueous solution, which is most often the case, the water in the electrolyte is reduced near the photoactive electrode by the electrons generated, producing hydrogen and OH - ions. The OH-ions thus produced will migrate towards the counter-electrode via the electrolyte, and the holes of the compound of formula (I) will be extracted via the ITO-type conductor and will enter the external electrical circuit. oxidation of OH- is carried out using the holes near the counter-electrode producing oxygen.The setting in motion of these charges (holes and electrons), induced by the absorption of light from the compound of Formula (I) generates a photocurrent The device can in particular be used as a photodetector, the photocurrent being generated only when the device is illuminated A photoactive electrode as described above can in particular be produced using a suspension, comprising the particles of a compound of formula (I) of the aforementioned type dispersed in a solvent, and depositing this suspension on a support, for example an ITO-coated glass plate or a metal plate, by the wet or any coating method, for example, by drop-casting, centrifugation (spin-coating), dipping (dip-coating), jet of ink or by screen printing. For more details on this subject, see R. R. Pasquarelli, D. S. Ginley, R. O'Hayre, Chem. Soc. Rev., Vol 40, pp. 5406-5441, 2011. Preferably, the particles based on a compound of formula (I) which are present in the suspension have an average diameter such as that measured by laser particle size (for example, by means of a Malvern type laser particle size which is less than 5 μm. According to a preferred embodiment, the particles of compound of formula (I) may be previously dispersed in a solvent, for example, terpineol or ethanol. The suspension containing the particles of compound of formula (I) may be deposited on a support, for example a conductive oxide coated plate.

According to a second variant of the invention which proves to be well suited to the production of photovoltaic devices, the compound of formula (I) is in the form of a continuous layer based on the compound of formula (I), the thickness of which is less than 50 μm, preferably less than 20 μm, more preferably less than 10 μm, for example less than 5 μm and typically greater than 500 nm.

By "continuous layer" is meant here a homogeneous deposit made on a support and covering said support, not obtained by simply depositing a dispersion of particles on the support.

The continuous layer based on a p-type compound of formula (I) according to this particular variant of the invention is typically placed in the vicinity of a n-type semiconductor layer between a hole conductive material. and an electron conducting material for forming a photovoltaic device for providing a photovoltaic effect.

An n-type semiconductor in the use according to the invention may be a conductive oxide, for example ZnO, or TiO 2, or a sulphide, for example ZnS. Furthermore, the term "layer based on the compound of formula (I)" means a layer comprising the compound of formula (I), preferably at least 50% by weight, or even at least 50% by weight. 75% by weight. According to one embodiment, the continuous layer according to the second variant consists essentially of the compound of formula (I), and typically comprises at least 95% by weight, or even at least 98% by weight, more preferably at least 99% by weight. by mass of the compound of formula (I).

The continuous layer based on a compound of formula (I) employed according to this embodiment can take several forms. The continuous layer may in particular comprise a polymer matrix and, dispersed within this matrix, particles based on a compound of formula (I), typically of dimensions less than 10 μm, or even less than 5 μm, in particular of the type of those used in the first embodiment of the invention. Typically, the polymer matrix comprises a p-type conductive polymer, which may especially be chosen from polythiophene derivatives, more particularly from poly (3,4-ethylenedioxythiophene) derivatives: poly (styrenesulfonate) (PEDOT: PSS). The particles based on the compound of formula (I) present in the polymer matrix preferably have dimensions less than 5 μm, which can in particular be determined by SEM. The invention will now be further illustrated with reference to the illustrative examples given below and the appended figures, in which: FIG. 1 is a diagrammatic sectional representation of a photoelectrochemical cell used in FIG. Example 4 described below; - Figure 2 is a schematic sectional representation of a photodetector device; Figure 3 is a schematic sectional representation of a photovoltaic device; - Figure 4 is a schematic sectional representation of a photovoltaic device according to the invention, not exemplified. FIG. 1 shows a photoelectrochemical cell 10 which comprises: a photoactive electrode 11 constituted by a support 12 based on a glass covered with a 2 cm × 1 cm ITO conductive layer on which has been deposited over the entire surface a layer 13 of thickness of about 1 pm based on particles of a compound of formula (I) according to the invention, the particles 14 have been previously dispersed in terpineol then deposited by coating ("Doctor Blade Coating" in English) on the conductive glass plate 11. - a reference electrode (Ag / AgCl) 15; and - a counter-electrode (platinum wire) 16; The three electrodes 11, 15 and 16 are immersed in an electrolyte 17 of KCI at 1M. The three electrodes are connected by a potentiostat 18. In FIG. 2 is shown a photodetector device 20 which comprises particles 21 of a compound of formula (I) according to the invention. This device comprises a layer 22 FTO of thickness of the order of 500 nm on which is electrodeposed a layer 23 of thickness of the order 1 pm based on ZnO. The layer 24 of thickness of the order of 1 μm based on the particles 21 of a compound of formula (I) according to the invention is deposited on the surface of the layer 23 by depositing drops from a suspension of particles of a compound of formula (I) according to the invention at 25-30% by weight in ethanol. A gold layer 25 of thickness of the order of 1 μm deposited on the layer 24 by evaporation. In Figure 3 is shown the photovoltaic device 30 which comprises particles 31 of a compound of formula (I) according to the invention. This device comprises a layer 32 FTO of thickness of the order of 500 nm on which is electrodeposed a layer 33 of thickness of the order 1 pm based on ZnO. The layer 34 of thickness of the order of 1 μm based on the particles 31 of a compound of formula (I) according to the invention is deposited on the surface of the layer 33 by depositing drops from a suspension of particles of formula (I) according to the invention at 25-30% by weight in ethanol. An electrolyte containing the pair of 12 / 1- redox mediator is deposited by depositing drops on the surface of the layer 34, and on which a gold layer 36 of thickness of the order of 1 pm being deposited by evaporation.

FIG. 4 shows photovoltaic device 40 which comprises a layer 41 based on particles of a compound of formula (I) according to the invention deposited on a layer 42 based on ZnO by coating, layer 42 based on ZnO being prepared by the sol-gel deposition, the layer 41 being in contact with a layer 43 of gold and the layer 42 based on the ZnO being in contact with a layer FTO 44. 3019539 R 2014/032 18 in contact with a compound of formula (I) according to the invention with an n-type semiconductor ZnO forms a pn junction. When the device is placed under a light source, the electrons generated go into the ZnO and the holes generated remain in the compound of formula (I) according to the invention. ZnO is in contact with FTO (electron conductor) to extract the electrons and the compound of formula (I) according to the invention is in contact with gold (conductor holes) to extract the holes. The following examples illustrate the invention without, however, limiting its scope. EXAMPLES EXAMPLE 1 BiCu 5A 50S - solid arrocyte reshaping procedure BiCu0.5Ag0.5S powder was prepared by reactive grinding at room temperature according to the following protocol: 1.028 g of Bi2S3 1.864 g of Bi 2 O 3, 0.477 g of Cu 2 S and 0.744 g of Ag 2 S are placed in an agate mortar in the presence of agate grinding beads. The mortar is then covered and placed in a Fritsch No. 6 planetary mill with a rotation speed of the order of 500 rpm. The grinding is continued for 120 min until a pure phase is obtained. The resulting compound C1, characterized by X-ray diffraction, has the following tetragonal mesh parameters: a = 3.866 Å, c = 8.5805 Å, V = 128.27 Å. EXAMPLE 20 Solid-Bromine BiCu0S0 95 Arbitration Procedure A BiCu0S0.510.5 powder was prepared by reactive grinding at room temperature, according to the following protocol: 1.028 g of Bi2S3, 1.864 g of Bi 2 O 3, 0.906 g of Cu 2 S and 0.114 g of Cul are placed in an agate mortar in the presence of agate grinding beads.

The mortar is then covered and placed in a Fritsch No. 6 type planetary mill with a rotation speed of the order of 500 rpm. The grinding is continued for 120 min until a pure phase is obtained.

The compound obtained C2, characterized by X-ray diffraction, has the following tetragonal mesh parameters: a = 3.88A, c = 9.595A, V = 129.47A. EXAMPLE 3 Process for Re-labeling BiCuo 7 Zno 30S-Arbro-Solid Compounds Biocontrol powder was prepared by reactive grinding at room temperature according to the following protocol: 0.720 g of Bi2S3, 1.584 g of Bi 2 O 3, 0.668 g of Cu 2 S and 0.349 g of ZnS are placed in an agate mortar in the presence of agate grinding beads.

The mortar is then covered and placed in a Fritsch No. 6 planetary mill with a rotation speed of the order of 500 rpm. The grinding is continued for 120 min until a pure phase is obtained. The compound obtained C3 characterized by X-ray diffraction has the following tetragonal mesh parameters: a = 3.870 Å, c = 8.571 Å, V = 128.36 Å. EXAMPLE 4 Method for Re-establishing BiCuo7Zn OS Articules with Soluble Recursors 1) Bismuth Precursor Solution (50mL at 0.1M): 4 mL of concentrated HNO3 (commercial 52.5%) is added to a vessel to 2.425 g BiNO3.5H20 and then diluted with 10 mL of water. In another beaker, 3 g of sodium hydroxide are mixed with 3 g of dibasic sodium tartrate (C 4 H 4 Na 2 O 6 - 2H 2 O). The two solutions obtained are mixed rapidly. A white precipitate forms and disappears immediately. The resulting solution is transparent in color. It is then diluted to a volume of 50 mL with water.

R 2014/032 2) Solution of the precursor of Copper I and Zinc (II) (50mL at 0.1M concentration of cation (Cu + Zn) 0.992 g of copper sulfate pentahydrate (CuSO4.5H2O) and 0.285 g of Zinc sulphate heptahydrate are dissolved in 30 ml of distilled water 1.5 ml of concentrated ammonia (28%) are added and a dark blue solution is obtained, 15 g of sodium thiosulfate pentahydrate are then added. The mixture is heated moderately (50 ° C) for four hours to give a colorless solution.It is preferable to use closed containers to avoid oxidation of Copper (I) 3) Na2S solution 12.25 g of Na2S.9H2O are dissolved in 100mL of distilled water. 4) Formation of the compound The previously prepared solutions containing Bi and (Cu (+ Zn) are mixed rapidly, a white precipitate forms and disappears immediately.The mixture is heated to a temperature of 90 ° C. The Na2S solution is heated. at 90 ° C. When both solutions are at the desired temperature, the solution of the cations (Bi, Cu, Zn) is added to the Na 2 S solution, a black precipitate is formed immediately, the solution is stirred at 90 ° C. After four hours, it is filtered, washed with distilled water and dried in an oven at 80 ° C. The product obtained has a single phase when it is observed by X-ray diffraction.

EXAMPLE 5 Use of the compounds C to C3 in a hot-electrochemical device The device described in FIG. 1 was used by polarizing the working electrode to a potential of -0.8 V vs Ag / AgCl. . The system is irradiated under an incandescent lamp (whose color temperature is 2700 K) alternating periods of darkness and periods of light. The intensity of the current increased when the system was placed in the light. It is a photocurrent which confirms the ability of each of the compounds C1 to C3 to generate a photocurrent. This photocurrent is cathodic (i.e., negative), which is consistent with the fact that each of these compounds C1 to C3 is a p-type semiconductor. For each of the compounds C1 to C5, the photocurrent values obtained are as follows: Photocurrent compound (pA.cm-2) Compound C1 75 Compound C2 150 Compound C3 100 R 2014/032

Claims (11)

REVENDICATIONS1. Material comprising at least one compound of formula (I): wherein M is a member or a mixture of elements selected from the group (A) consisting of Pb, Sn, Hg, Ca, Sr, Ba. , Sb, In, TI, Mg, rare earths, M 'is a member or a mixture of elements selected from the group (B) consisting of Ag, Ti, V, Cr, Mn, Fe, Co, Ni, Zn , Ga, Mg, Al, Cd, M "is a halogen, x, y and z are numbers less than 1, in particular less than 0.6, especially less than 0.5, with at least one of the numbers x, y or z not zero, and 0 5 c <0.2. 2. Process for the preparation of a material according to claim 1, comprising a step of solid grinding a mixture comprising at least inorganic compounds of bismuth and copper, and optionally at least one oxide, sulfide, oxysulfide, halide or oxyhalogenide. at least one element selected from Bi and the elements of the group (A), and optionally at least one oxide, sulfide, oxysulfide, halide or oxyhalide of at least one element selected from Cu and the elements of the group (B) . 3. Process for the preparation of a material according to claim 1, comprising a precipitation reaction, characterized in that it comprises the following steps: (a) preparation of at least one solution comprising metal precursors in the form of at least one salt of the inorganic bismuth compounds, and optionally at least one oxide, sulfide, oxysulfide, halide or oxyhalide of at least one element selected from Bi and the elements of group (A) consisting of Pb, Sn, Hg, Ca, Sr, Ba, Sb, In, Ti, Mg, rare earths, and R 2014/032 (b) preparation of at least one solution comprising metal precursors in the form of at least one salt of inorganic copper compounds , and optionally at least one oxide, sulfide, oxysulfide, halide or oxyhalide of at least one element selected from Cu and the elements of group (B) consisting of Ag, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Mg, Al, Cd, and, (c) optionally preparing at least a solution comprising a source of sulfur, (d) blending by precipitation of the solutions obtained after steps (a), (b) and optionally (c), (e) filtration, and washing if necessary, of the compound of formula (I) obtained at the end of step (d). 4. Process for the preparation of a material according to claim 1, comprising the following steps: (a ') providing a mixture comprising at least, in the dispersed state, inorganic compounds of bismuth and copper and, optionally at at least one oxide, sulphide, oxysulfide, halide or oxyhalide of at least one element selected from Bi and the elements of group (A), and optionally at least one oxide, sulphide, oxysulphide, halide or oxyhalide of at least one selected element; among Cu and the elements of the group (B), and optionally a source of sulfur, (b ') dissolving the mixture in water or an aqueous medium under hydrothermal conditions and preferably with stirring, and (c') cooling of the resulting solution, whereby particles of the compound of formula (I) Bil_xMxCui_y_EM'yOS1.2M "Z are obtained. 5. Use of a material according to claim 1 as a semiconductor, in particular for photoelectrochemical or photochemical application, in particular to provide a photocurrent. 6. The use according to claim 5, wherein the compound of formula (I) is employed in the form of isotropic or anisotropic objects having at least one dimension less than 50 μm, preferably less than 20 μm. 7. Use according to claim 6, wherein the compound of formula (I) is employed in the form of particles smaller than 10 μm in size. 8. Use according to claim 7 wherein the compound of formula (I) is in the form of platelet-type anisotropic particles, or agglomerates of a few tens to hundreds of such particles. 9. Use according to claim 6, wherein the compound of formula (I) is in the form of a continuous layer based on a compound of formula (I) whose thickness is less than 50 μm, preferably less than 50 μm. 20 μm, wherein the layer based on a compound of formula (I) is a layer comprising at least 95% by weight of compound of formula (I). 10. Use according to claim 6, wherein the compound of formula (I) is in the form of a continuous layer based on a compound of formula (I) whose thickness is less than 50 μm, preferably less than 50 μm. 20 μm, where the layer based on a compound of formula (I) comprises a polymer matrix and, dispersed within this matrix, particles based on a compound of formula (I) of dimensions less than 5 μm. Photovoltaic device comprising, between a hole-conducting material and an electron-conducting material, a layer based on a compound of formula (I) according to claim 1, of type p, and a layer based on a n-type semiconductor, wherein: the p-type compound (I) compound layer is in contact with the n-type semiconductor layer; the p-type compound (I) compound layer is in proximity to the hole conductive material; and the n-type semiconductor layer is in proximity to the electron-conducting material.